The use of radioisotopes for various medical procedures such as brachytherapy and the like is well known. Such uses fall into two general categories: (i) high dose radioisotopes which are temporarily positioned in relation to a patient's body for a relatively short period of time to effect the radiation treatment; and (ii) low dose radioisotopes which are permanently implanted in a patient's body with the duration of the radiation treatment determined by the strength and half-life of the radioisotope being implanted.
High dose radioisotopes are typically implanted using a catheter arrangement and a device commonly known as an after loader that advances the high dose radioisotope located on the end of a source wire through the catheter to the desired location. Low dose radioisotopes, on the other hand, are implanted using an array of implant needles with the low dose radioisotopes being encapsulated in very small containers known as seeds that are manually loaded into a series of implant needles and then ejected to form a three-dimensional grid of radioisotopes in the patient that corresponds to a dose plan as determined by the physician.
The goal of the low dose brachytherapy procedure is to position this three-dimensional grid of radioisotopes seeds in and around a target cancerous tissue area. Each of the radioisotope seeds consists of a radioactive source such as Iodine (I-125) or Palladium (Pd-103) inside a small tube-like titanium shell that is about the size of a grain of rice. These types of low dose radioactive sources emit a very low energy radiation that is primarily absorbed by the tissue immediately surrounding the radioisotope seed. This constant low energy radiation is typically emitted by the radioisotope seeds for a period of up to six months as a way to kill the cancer cells in the target area without having to subject the patient to the discomfort and risks that often accompany high dose radioisotope procedures.
One common brachytherapy procedure is the use of low dose radioisotopes to treat prostate cancer. Although brachytherapy procedures using low dose radioisotopes can be applied to many different parts of the body, it is helpful to describe a particular treatment to gain a better understanding of these treatments. In a typical prostate cancer procedure, a predetermined number of seeds (between 1-6) are positioned within each of a series of implant needles (up to 40), with the seeds being spaced apart in each needle by small spacers. A small amount of bone wax is positioned on the tip of the implant needles to prevent the seeds and spacers from falling out until they are implanted in the patient.
The loaded implant needles are positioned at the appropriate location for insertion into the perineal area of the patient using a stand that has an X-Y coordinate grid. Each needle is manually positioned in the appropriate chamber in the grid and is inserted into the patient. An ultrasound probe is used to assist the physician in guiding each of the needles to the desired location. The seeds and spacers are delivered from the tip of the implant needle using a stylet and hollow needle arrangement where the hollow needle is preferably retracted while the stylet remains in place. When completed, the implanted seeds form a three-dimensional grid of radioisotope sources that implements a predetermined dose plan for treating the prostate cancer in the patient. For a more detailed background of the procedures and equipment used in this type of prostate cancer treatment, reference is made to U.S. Pat. No. 4,167,179.
There have been numerous developments in the design of equipment for use in low dose radioisotope procedures. U.S. Pat. Nos. 5,626,829, 5,682,892, 5,868,757, 5,931,786, 5,957,935 and 5,961,527 describe improvements in the stands and grids used to stabilize and guide the manual placement of needles during a low dose radioisotope procedure. U.S. Pat. Nos. 4,586,490 and 4,627,420 describe manually operated implanting devices that substitute for the conventional implant needles. U.S. Pat. Nos. 5,928,120 and 5,938,583 describe improvements to the conventional implant needles themselves. U.S. Pat. Nos. 4,763,642 and 4,815,449 describe a bioabsorbable carrier for implanting a string of low dose radioisotope seeds. U.S. Pat. Nos. 4,086,914, 5,242,373, 5,860,909, 6,007,474, 6,102,844, and 6,213,932 describe manual seed injector arrangements for a low dose radioisotope procedure that utilize drop-in seed cartridges or seed magazines to supply the seeds directly to an implant needle that is specifically adapted to such cartridges or magazines.
U.S. Pat. No. 6,221,003 describes an elongated cartridge with a central channel that contains a plurality of seeds interspersed with a plurality of spacers for loading a single implant needle; however, the seeds and spacers are manually loaded into the central channel using leaded gloves or tweezers. U.S. Pat. No. 6,280,472 describes an orbiturer for manually pushing seeds from a central channel into tissue such that the implants are selectably spaced from one another via a reciprocating carriage arrangement. The orbiturer also includes a mechanical detent arrangement that serves as an indicator of the number of seeds that were implanted. PCT Publ. No. WO 01/66185 describes an alternative arrangement for loading a single implant needle in which a separate seed cartridge and spacer cartridge are manually advanced into corresponding slots in a loading tube such that a manually-operated plunger can dislodge the seed and spacer from chambers in the cartridges to load the implant needle.
Over the years there also have been numerous advancements in the design of equipment for use in high dose radioisotope procedures. U.S. Pat. Nos. 3,861,380, 4,851,694, 5,092,834, 5,120,973, 5,183,455, 5,272,349, and 5,800,333 describe various automated afterloaders that advance a source wire carrying a high dose radioisotope at the end into a catheter system for high dose radioisotope procedures. U.S. Pat. Nos. 4,150,298, 5,147,282, 5,851,172 and 6,048,300 describe replaceable cartridge assemblies that contain the source wire used in conjunction with specifically adapted afterloaders.
Although the use of replaceable cartridges and automated afterloaders have been well received for use in connection with high dose radioisotope procedures, the standard techniques for low dose radioisotope procedures continue to utilize a series of implant needles that are manually loaded by a radiophysicist at the hospital just prior to the time they are manually inserted by the physician. There are several reasons for why this manual process has been the standard for low dose radioisotope procedures.
The differences in the types of radioisotope sources do not favor the use of existing manual drop in cartridges for low dose radioisotope procedures. The source wires used for high dose radioisotope procedures use only one or a small number of very high power radioisotope sources having relatively long half-lives. As a result, it is cost effective and practical to provide for a cartridge arrangement for such a small number of high dose radioisotopes that can be preordered and maintained at the hospital well in advance of a procedure. In contrast, low dose radioisotope procedures have relatively short half-lives of the radioisotopes and it is preferable that the radioisotope seeds be sent to the hospitals just prior to their use. Because the number of radioisotope seeds varies from procedure to procedure depending upon the dose plan, and because the cost of each low dose radioisotope seed is significant, it is not cost effective to order many more radioisotope seeds than will be used in a given procedure.
It is important to minimize the time of the procedure, both in terms of the exposure time of the physician to the low dose radioisotope seeds and in terms of the total time of the procedure from the economics of medical practice. In the case of brachytherapy treatment for prostate cancer, it is also advantageous to complete the procedure as quickly as possible because the prostate gland can swell during the procedure, further complicating the implantation process. The existing drop-in cartridge and seed magazine manual systems described above for low dose radioisotope procedures generally require a longer time to perform the implant procedure than when conventional preloaded implant needles are used. This is because the radioisotope seeds are manually implanted one-by-one, rather than being delivered simultaneously as a group from a preloaded needle. The manual one-by-one techniques also can require more care and precision to insure that all of the seeds for a given row are actually implanted in that row.
Due to the large number of low dose radioisotope seeds used in a given procedure (typically up to 150), the requirement that a radiophysicist at the hospital take a set of sample measurements of the strength of the radioisotope seeds to confirm that the seeds meet the requirements specified by the dose plan, and the need for the implanting physician to be able to modify the dose plan at the time of implant, it is generally considered that the flexibility afforded by manually loading the implant needles just prior to the operation provides the best possible treatment procedure for the patient and the most economically efficient procedure for the hospital.
More recently, systems that attempt to integrate the diagnostic process of establishing a dose plan using an ultrasound probe with a manual implant needle grid have been proposed. The process of establishing a dose plan for brachytherapy treatment is described, for example, in U.S. Pat. No. 6,095,975. In U.S. Pat. No. 5,871,448, a manual stepper arrangement for positioning the ultrasound probe is described. In U.S. Pat. No. 6,206,832, an apparatus for merging multiple ultrasound image to assist in guiding implant needles is described.
In U.S. Pat. No. 6,129,670, an automated arrangement is described for utilizing the ultrasound probe to generate ultrasound image data that is used to generate a translucent volume image of the patient's body and the prostate over which an image of the implant needles can be superimposed. One embodiment of this patent briefly describes an automated system for loading radioisotope seeds into implant needles based on a clinical plan that enables rapid treatment based on substantially real-time preplanning using rapid patient organ evaluation. In this embodiment, a gravity fed bin arrangement selectively drops seeds into the rear end of a vertically oriented needle. A pair of micro-controllers communicates with the computer that generated the dose plan to be the dose plan and control the dropping of the seeds and spacers into the rear end of the needle by using an optical sensor positioned along the passageway through which the seeds are dropped to monitor loading of each seed into the needle. Although the needle loading is proposed to be automated in this manner, the implantation of the loaded needles is accomplished manually using a conventional needle grid arrangement.
A modular device for implanting radioactive seeds through a needle implanted in the body is described in EP 1 070 519 A1. An electronic control device controls a pushing drive, a seed supply container, a spacer supply container and a multi-channel holder for seed-spacer trains. A tube connects the multi-channel holder and the needle through which the seed-spacer trains are pushed by a wire in order to implant them in the body, with the wire remaining in place while the needle is withdrawn. In one embodiment, the seed-spacer trains are loaded and implanted by a single unit. In another embodiment, the seed-spacer trains are preloaded into the multi-channel holder by a loading unit and then the multi-channel holder is then transferred to an implantation unit. In this embodiment, a microprocessor is used to control the seed loading unit in response to a therapy planning program. Like U.S. Pat. No. 6,129,670, the loading of seeds and spacers to form the seed-spacer trains in EP 1 070 519 A1 is accomplished directly in response to the therapy planning program executed that determines how the needles are to be placed in the prostate and how many radioactive seeds are to placed in what order in each of the needles.
Other uses of automated arrangements for positioning ultrasound probes or for controlling biopsy needles have been proposed. U.S. Pat. Nos. 4,649,925, 5,181,514, 5,282,472, 5,361,768, 5,540,649, and 5,552,645 describe the use of automated arrangements for positioning of ultrasound probes. These automated arrangements typically include a stepper motor for advancing and retracting the ultrasound probe within the rectum and a rotational control for rotating the probe once in position within the rectum. U.S. Pat. Nos. 5,398,690, 5,415,169, and 5,830,219 describe automated biopsy arrangements in which a biopsy needle is inserted under automated control to obtain and extract a biopsy sample. These automated systems also include a single linear motion control and a rotational component control, and have an additional angulation control that controls the orientation of the needle upon insertion.
More complicated and expensive three-dimensional automated control systems for surgical instruments also have been developed. U.S. Pat. Nos. 5,540,649 and 5,695,500 describe examples of automated surgical systems that feature multiple joints and arms to allow for control of motion in all three axis of a surgical instrument positioned at the working end of these systems. The complexity and expense of these three-dimensional control systems have generally precluded their use in connection with positioning systems for ultrasound probes and biopsy needles.
Despite these improvements, the manual processes for low dose radioisotope procedures remains the standard for the reasons described above. It would be advantageous to provide for an automated implantation system for implanting low dose radioisotope seeds in a patient as part of a brachytherapy procedure that could overcome these problems and enhance the safety and efficiency of this process.